As information communication technologies have rapidly developed in recent years, services for providing multimedia contents containing a large amount of data are becoming widespread. As one of forms for providing such multimedia contents, there has been proposed a form of movie activities called “digital cinema” that uses digital information for shooting and screening, instead of a form which uses conventional films for the shooting and screening. Standardization organizations such as Digital Cinema Initiative, LLC (Limited Liability Company) have been established for such digital cinema.
According to the digital cinema, such a form is expected that edition is performed after digitizing the image in the image-taking process, and screening is performed by distributing it to movie theaters over a network. The use of such digital data can prevent deterioration of images that may occur due to age deterioration of films and mechanical damages caused by screening.
Ideally, it is has been desired to conserve permanently the movie contents that have great value as cultural properties. In the conventional film movies, the quality of the movie contents themselves has been kept by reprinting the films, e.g., every year.
Conversely, the digital information is stored by storing them on various recording mediums such as magnetic tape, magnetic disc, optical disc, magneto-optical disc or flash memory. However, these recording mediums have a limited life. For example, it has been that the optical discs such as CD (Compact Disc) and DVD (Digital Versatile Disc) have the life of several tens of years because a recording layer made of aluminum or the like corrodes due to intrusion of atmosphere. In the recording medium such as magnetic tape or magnetic disc (e.g., hard disc or flexible disc) of the type that records data using the magnetism, the magnetism itself naturally decays with time, and further is liable to be affected by external magnetic field so that it is practically difficult to keep the data storage for a long term. In the recording medium such as a flash memory of the type that uses electric charges for storing the data, the charges themselves naturally decay with time and are liable to be affected by external magnetic field so that it is practically difficult to keep the data storage for a long term.
As stated above, these recording mediums that are now widespread cannot practically hold the data for a long term, and require further reproduction or duplication at predetermined intervals, similarly to the conventional films.
Accordingly, semiconductor storage devices such as a mask ROM (Read Only Memory) have been expected as recording mediums having a longer life. Such semiconductor storage devices are made of silicon that is physically and chemically stable, and therefore are hardly affected by corrosion and the like. For example, Japanese Patent Laying-Open No. 2006-237454 (Patent Document 1) has disclosed a structure and a manufacturing method of the above mask ROM.    Patent Document 1: Japanese Patent Laying-Open No. 2006-237454